Cathodic protection of metal structures



Jan. 20, 1959 R. H. M CALL 2,370,079

CATHODIC PROTECTION OF METAL STRUCTURES Filed Nov. 16, 1954 33 law M4175? 4/ NY 35 27 M424 /9 I I L i 'CATHODIC PROTECTION OF METAL STRUCTURES Richard H. Mctlall, Houston, Tex., assignor to The Texas Company, New York, N. Y., a corporation of Delaware The present invention relates to a novel device for cathodically protecting against corrosion a metal structure located in the water, such as a pier or an oil well drilling platform.

Cathodic protection of such structures against corrosion has been employed for some time, using sacrificial metal anodes of a metal or alloy which has a higher anodic solution potential than does the metal of the structure. Ordinarily such structures are composed of iron members, and the sacrificial metal anode then advantageously is formed of such metals as zinc, aluminum, magnesium, or alloys of these metals with one another. Magnesium and its alloys are particularly advantageous because of their high anodic solution potential to ordinary steel, which ranges from 0.7 to 1.3 volts. Metals above magnesium in the electro chemical series usually are not advantageous because they react so rapidly with water as to have an undesirably short life.

In accordance with the prior art sacrificial metal anodes have been used by suspending them vertically by means of cables attached to the structure. Large structures require dozens of anodes for adequate protection; and each of these anodes in the past has been suspended tent from its own cable, thus making a complicated and expensive arrangement which is diflicult to install initially and difficult to service subsequently. Also, the electrolytic action set up between an anode and its suspending cable may be such as to cause separation of the anode from the cable, with resultant loss of the anode and reduction in corrosion protection.

In accordance with the present invention, cathodic protection of .a metal structure located in water is accomplished by a series of anode units detachably linked or coupled together in a string which is electrically connected only at its ends to the structure in such a way that the anodes hang in the water.

Each anode unit comprises a body of metal having a higher anodic solution potential than the metal of the structure. An elongated supporting member such as a rod, cable, or chain extends from the body for connecting it to an adjoining anode unit, and means is also carried by the body for connecting it to a second adjoining anode unit. Quick-acting couplings are provided so that the anode units of the series can be quickly connected and disconnected to one another at will when replacement is necessary.

When the elongated supporting member is made of a metal such as iron having relatively poor electrical conductivity, each anode unit also advantageously comprises a conductor of a metal such as copper, aluminum, or silver having good electrical conductivity which extends from the anode to a point adjacent the end of the supporting member, electrically bridging the supporting member and assuring good conduction of the generated electricity.

The principles of the invention will be described in more detail below, with reference to the drawings where- 2,870,979- Patented Jan. 20, 1953 shore oil well drilling platform cathodically protected in.

accordance with the invention;

Fig. 2 is a side elevational view of an anode unit constructed in accordance with the invention; and

Fig. 3 is a side elevational view of a modified form of anode unit. 4

As shown in Fig. 1, an cit-shore oil well drilling platform 11 having three iron supporting columns 13, 15, and 17 embedded in the floor 19 of a body of water such as the Gulf of Mexico, is protected against corrosion by a string 21 of coupled magnesium anodes 23, 25, 27 and 29, all connected together by iron supporting chains,- as 31, 33, 35, and 36.- Each of the chains is provided with a quick-acting terminal coupling member for connecting it either to the adjoining anode unit, as at 3'7, or to a column stud as at 39. Each anode unit also includes wires, such as at 41, 42, 43, and 44, of electrically conducting material such as copper, which extend from an anode such as 29 to a point adjacent the ends of the chains such as 31, and 33, to which the wire is attached firmly as by brazing.

With the described structure a string 21 of anodes can be prepared on the platform 11 or on the deck of a vessel, and then secured to the structure simply by attaching the two ends of the string to the columns as at 39 and 45. The columns may be provided with apertures, studs, hooks or the like to facilitate attachment. When servicing is required it is only necessary to detach the ends of the string from the columns, place the string on the deck of a vessel or on the platform. Rapid replacement of any consumed anodes is then accomplished by uncoupling the appropriate chains from one another and replacing each removed unit with a complete new unit. Thus, many anodes can be serviced in one operation, instead of having to service separately a great number of individually suspended anodes as in the past.

Details of an anode unit are shown in Fig. 2. An iron chain 51 carries at each end a quick-acting coupling such as snap hooks 53 and 55. Extending between the two snap hooks is an electrical conductor wire 57 WhlCh 1s brazed or otherwise electrically connected to the snap hooks. Improvement in the electrical conductivity of the unit also is obtained by brazing a continuous layer of bronze on the snap hooks themselves so that good elec-v trical conductivity is assured when each unit is coupled to its neighbors.

Around the middle portions of chain 51 and wire 57 there is integrally cast a body of the anode metal, such as magnesium, which thus securely adheres to the chain and to the wire. Casting may be accomplished by enclosing the chain and wire portions in a conventional mold which is then filled with molten metal. With this integral construction there is no danger of losing the anode from its supporting chain by electrolytic action.

Obviously two chains and two wires can have their unconnected end portions incorporated in a metal casting in a similar manner.

In the modified form of anode unit shown in Fig. 3, an anode 63 is cast around a chain 65 and wire 67 near the ends thereof, instead of at the middle as in Fig. 2. The resulting unit has a long chain 65 extending from one end carrying a snap hook 69 for coupling it to the next unit. The other end of the anode, however, only has a short chain link projecting therefrom and forming a coupling eye 71 for attachment to the next unit in a string.

It is evident that a string 21 of anodes as shown in Fig. 1 can be readily formed from a series of units of the type shown in Fig. 2, having coupling devices 53 and 55 on both ends of the protruding chain 51. It is sometimes more economical, however, to use adevice such.

as that of Fig. 2 only at one end of the string, as by connecting it to the structure at 39, and then to form the rest of the stringwithunits similar to that shown in Fig. 3. Thus, for example, a unit such as that of Fig. 2 can be secured to structure 11 at 39 by snap hook 55, and can be secured to the next adjacent anode unit by coupling the snap book 53 to a protruding; eye 71 as in Fig. 3. The snap hook 69 can then be coupled tothe eye of the next unit, etc., etc., with the snap hook of the last unit engaging the column: 17.

From the foregoing, description it is apparent that there has been provided an improved method and device for cathodically protecting off-shore structures which is simple and inexpensive in construction, which is easy to service, and whichtwill not have its elficiency reduced by the loss of anodes due to electrolytic separation from their supporting members.

Obviously many modifications and variations of the invention, as hereinbefore set forth, maybe made without departing from the spirit and scope thereof, and therefore only su h limitation should be imposed as are indicated in the appended claims.

I claim:

1. An anode unit for cathodically protecting from corrosion a structure of ferrous metal located in water, said unit comprising an anode body, said anode body being composed of metal selected from a group consisting of aluminum, magnesium, zinc and alloy mixtures thereof; an elongated chain being composed offerrous metal having a part thereof integrally cast within said anode body and extending fromopposite sides of said anode body as a flexible supporting member, each of the opposite ends of said chain carrying a snap-hook coupling member for connecting said anode unit to an adjoining member, said snap-hool coupling member being composed of metal having a continuous layer of bronze brazed thereon; an elongated conductor wire co-extensively extending the length of said chain in substantial parallel relationship thereto and having a part thereof integrally 1 cast within said anode body, each of the opposite ends of said conductor Wire being brazed to said snap-hook coupling member adjacent thereto, said conductor wire being composed of metal selected from the group consisting of aluminum, copper and silver.

- 2. In combination, a structure of ferrous metal located.

in water and a string of anodes having its opposite ends connected to said structure at positions remote from one another, said string comprising a plurality of anode units detachably coupled to one another in spaced relationship to one another lengthwise of said string, each of said anode units comprising an anode body, said anode body being composed of metal selected from the group consisting of aluminum, magnesium, zin and alloy mixtures thereof; an elongated chain being composed of ferrous metal having a part thereof integrally cast within said anode body and extending from opposite sides of said anode body as a flexible supporting member, each of the opposite ends of said chain carrying a snap-hook coupling member for connecting said anode unit to an adjoining member, said snap-hook coupling member being composed of metal having a continuous layer of bronze brazed thereon, an elongated conductor wire coextensively extending the length of said chain in substantial parallel relationship thereto and having a part thereof integrally cast within said anode unit, each of the opposite ends of said conductor Wire being brazed to said snap-hook coupling member adjacent thereto, said conductor wire being composed of metal selected from the group consisting of aluminum, copper and silver.

References Cited in the file of this patent UNITED STATES PATENTS 752,844 Kinnear Feb. 23, 1904 1,489,743 Delius Apr. 8, 1924' 1,709,523 Delavie et a1. Apr. 16, 1929 2,444,174 Tarr et al. June 29, 1948 2,486,936 Fergus Nov. 1, 1949 2,508,171 Kaufman May 16, 1950 2,571,062 Robinson et al. Oct. 9, 1951 2,619,455 Harris Nov. 25, 1952 2,743,227 Waite et al. Apr. 24, 1956 2,763,907 Douglas Sept. 25, 1956 2,775,554 Jorgensen Dec. 25, 1956 FOREIGN PATENTS 17,759 Great Britain Aug. 28, 1913 

1. AN ANODE UNIT FOR CATHODICALLY PROTECTING FROM CORROSION A STRUCTURE OF FERROUS METAL LOCATED IN WATER, SAID UNIT COMPRISING AN ANODE BODY, SAID ANODE BODY BEING COMPOSED OF METAL SELECTED FROM A GROUP CONSISTING OF ALUMINUM, MAGNESIUM, ZINC AND ALLOY MIXTURES THEREOF; AN ELONGATED CHAIN BEING COMPOSED OF FERROUS METAL HAVING A PART THEREOF INTEGRALLY CAST WITHIN SAID ANODE BODY AND EXTENDING FROM OPPOSITE SIDES OF SAID ANODE BODY AS A FLEXIBLE SUPPORTING MEMBER, EACH OF THE OPPOSITE ENDS OF SAID CHAIN CARRYING A SNAP-HOOK COUPLING MEMBER FOR CONNECTING SAID ANODE UNIT TO AN ADJOINING MEMBER, SAID SNAP-HOOK COUPLING MEMBER BEING COMPOSED OF METAL HAVING A CONTINUOUS LAYER OF BRONZE BRAZED THEREON; AN ELONGATED CONDUCTOR WIRE CO-EXTENSIVELY EXTENDING THE LENGTH OF SAID CHAIN IN SUBSTANTIAL PARALLEL RELATIONSHIP THERETO AND HAVING A PART THEREOF INTEGRALLY CAST WITHIN SAID ANODE BODY, EACH OF THE OPPOSITE ENDS OF SAID CONDUCTOR WIRE BEING BRAZED TO SAID SNAP-HOOK COUPLING MEMBER ADJACENT THERETO, SAID CONDUCTOR WIRE BEING COMPOSED OF METAL SELECTED FROM THE GROUP CONSISTING OF ALUMINUM, COPPER AND SILVER. 